In the field of IT security, the property of so-called functional safety is regarded as present if a system behaves in conformance with the expected functionality. Information security, in contrast, relates to the protection of the technical processing of information. Information security measures, in this terminological sense, are used to prevent unauthorized data manipulation or the divulging of information.
A message authentication code is used in this context to provide security concerning the origin of data or messages, and to check their integrity. For this purpose, first the sender and receiver agree on a secret key. The sender calculates a message authentication code for this key and for his message, and then sends the message and the message authentication code to the receiver. The receiver calculates the message authentication code for the received message using the key, and compares the calculated message authentication code to the received one. Agreement of the two values is interpreted by the receiver as a successful integrity test: the message was sent by a party who knows the secret key, and the message was not changed during the transmission.
German Patent Application No. DE 10 2009 002 396 A1 describes a method for protection against manipulation of a sensor and of sensor data of the sensor, and a sensor for this purpose, in which, in the context of authentication, a random number is sent from a control device to the sensor, and, for recognition of a manipulation of the sensor data, the sensor data from the sensor to the control device are provided with a cryptographic integrity protection, and, in order to prevent replay attacks, additional time-variant parameters are added to the sensor data, which the sensor data will send from the sensor to the control device with the integrity protection and the added time-variant parameters. Here, after the authentication of the sensor the random number, or a part of the random number, or a number obtained from the random number using a function, are used for the time-variant parameters.